In MRI it is often desirable to excite and receive a signal from multiple excited slices (or volumes). Interleaved multi-slice imaging is very efficient, as different slices can be excited and imaged while magnetization from other slices recovers. However, the desired TR and TE for contrast, as well as the time required to play pulses for a given slice and number of slices force certain constraints on how slices are interleaved. Additionally, for T1-weighted imaging, the number of slices that can be interleaved within the desired repetition time (TR) is often limited. This leads to suboptimal contrast if TR is increased to accommodate all slices, or increased scan time if multiple acquisitions are needed.
What is needed is highly flexible approach to ordering slices for interleaved imaging.